Process and device for heating a moving web

ABSTRACT

The process for heating a moving web, in particular a corrugated board web, in addition to a supply of heat to the one outer side of the moving web, also provides supply of heat to the other outer side of the web (5). A preheater (1) with a first heating face (3), which is associated with a movable deflection roll, is connected to a second heating face (13) connected to the deflection roll (10). With its other outer side, the web (5) is guided via this second heating face.

BACKGROUND OF THE INVENTION

The invention relates to a process for heating a moving web, inparticular a corrugated board web, as well as a preheater.

A preheater for a corrugated board web has been disclosed by DE 23 02449. This known preheater has a heating drum that is driven to rotate.The web is supplied via a stationary inlet to the heating drum and iscarried away from it via a stationary outlet. The heating drum isassociated with a deflection roll for the web, which can be pivotedconcentrically around the central axis of the heating drum. The pivotangle determines the contact area of the web on the heating drum andtherefore the heat quantity to be transmitted. The pivoted deflectionroll carries the web along and moves it over the heating drum, whereinthe winding angle can be adjusted. This produces the heat transfer fromthe heating face of the drum into the adjoining outer layer of the web.In order to prevent the incoming web from touching the outgoing web,normally a second roll is provided in the circumference direction of theheating drum. For safety reasons, these rolls are spaced apart from therotating heating drum by 120 mm. It is disadvantageous that the web canonly wind around the heating drum with a maximal angle of approximately270°. Furthermore, the web can only be heated on one side by the heatingdrum, by means of which an uneven heating of the web takes place. Thereis also the danger that at high web speeds, due to the merely unilateralweb heating, the adhesive applied in the adjoining adhesive mechanismdoes not set, i.e. develop a certain adhesive effect, rapidly enough.

SUMMARY OF THE INVENTION

The object of the invention is to establish a process and a device forheating a moving web, in particular a corrugated board web, by means ofwhich it successfully increases the heating face without requiring morespace and with a reduced construction cost. At the same time, anincreased supply of heat and a more rapid heat transfer to adhesiveapplication point should be made possible.

The invention eliminates the danger of intake between the deflectionroll and the heating drum so that the safety distance prescribed by lawbetween the deflection roll and the heating drum does not have to beheeded. In addition, the effective heating area is increased accordingto the invention, with a reduced space requirement and a reduced cost.Finally, the possible regulating range for the heat transfer isbroadened. Also, the maximal winding angle of the heating drum can beenlarged by means of the web.

According to one embodiment of the invention, in a preheater of a knowntype, the rotary heating drum is associated with a heating face in theshape of a circular segment that is connected to the deflection roll sothat it can be moved concentrically to the heating drum, wherein theother outer side of the web is guided via this circular segment-shapedheating face and rests against it.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in detail below in conjunction with anexemplary embodiment represented in the drawings.

FIG. 1 shows a partially sectional schematic representation of apreheater according to the invention, with the minimum winding angle ofthe web around the heating drum in connection with a unilateralcorrugated board machine and

FIG. 2 shows a view of a preheater like the one in FIG. 1, with themaximal winding angle of the web around the preheating drum.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preheater 1 according to FIGS. 1 and 2 has a heated drum 2 with asmooth surface. This can be internally heated, e.g. by means of steam orin some other way. The drum 2 can be driven in the indicated arrowdirection. However, it can also be supported merely so that it canrotate. The drum jacket 3 is comprised of highly heat-conductingmaterial, preferably steel. The drum 2 is supported on both ends inbearing plates 4.

The web 5, e.g. a cover web for a unilateral corrugated board web,travels via an inlet 7, which is embodied, for example, as a stationarypair of rolls, toward the drum 2 in the indicated arrow direction.

According to FIG. 1, the web 5 rests against the heated drum jacket 3and winds around it with the smallest possible winding angle, e.g. 72°.

On its way out, the web 5 is guided via a deflection face 10, e.g. arotary deflection roll 11. From the roll 11, the web 5 travels furtherto a stationary outlet 12. According to FIG. 1, the web 5 travels to aunilateral corrugated board machine 20, for example. In this connection,the guide roll 21 can cooperate with the press roll 22. This press rollcooperates in the usual manner with the corrugator roll 23 and theadhesive transfer roll 25 transfers the adhesive from the adhesivemechanism, not shown, onto its corrugated paper web 24, which adhesivetransfer roll 25 is disposed at a foot 17 with an insert guide.Naturally, the outlet 12 can also be embodied in other ways.

The deflection face 10 is connected to a heating face 13, which iscomprised of a heatable circular segment 14 made of metal, which isdisposed concentric to the central axis of the drum 2.

The heating face 13 and the deflection face 10, which is embodied in theconcrete exemplary embodiment as a deflection roll 11, are disposed sothey can be pivoted together around the central axis of the drum 2.

For this, the deflection roll 11 and the heating face 13 can beconnected to circular disks 30 that can be rotated around the centralaxis of the heating drum 2 and can be moved by means of an adjustingdevice, e.g. by means of chains.

In FIG. 1, the deflection roll 11 with the heating face 13 is disposedin a position with the smallest winding angle, e.g. 72°. The web 5 doesnot travel via the heating face 13.

In addition to the one outer side of the web 5 (in a unilateralcorrugated board web, the corrugated web 7'), if the intent is to heatthe other outer side of the web (in a unilateral corrugated board web,the smooth web 6), then as can be seen from FIG. 2, the deflection face10 with the heating face 13 is pivoted clockwise around the central axisof the drum 2. The size of the pivot angle depends on the heat to betransmitted into the web 5. The pivot angle can be adjusted manually orautomatically, e.g. as a function of web moisture, web temperature,and/or web speed.

The incoming web 5 defines the maximal pivot angle.

Due to the pivoting of the deflection face 10 with the heating face 13,the web 5 winds more and more around the drum 2 and it returns in theopposite direction, pressed against the heating face 13. After leavingthe heating face 13, the web 5 travel to the outlet 12.

The heating face 13 can be provided with meandering heating conduits 15or electrical heating wires. A hot medium, e.g. a heating steam, can beguided through the heating conduits.

The roll 11 can be rotated as the deflection face 10. It can also bedriven if need be.

The separable foot 17 of the lateral plates 4 is disposed as close aspossible to the imaginary circular path of the circular segment 14. Thefoot 17 can, for example, directly receive an insertable adhesivemechanism 17 or the like, not shown, which is disposed underneath it. Asa result, the heated drum 2 and the heating face 13 are positioned veryclose to the adhesive transfer point on the circumference of theadhesive transfer roll 25. By means of this, an unnecessary heat loss isprevented during the movement of the web 5 from the preheater 1 to theadhesive transfer point. The space requirement is reduced.

What is claimed is:
 1. A process for heating a moving web having firstand second faces, comprising the steps of:heating the first and secondfaces of the web by deflecting the web from a first heating devicecomprising a drum having a first, curved heating face that heats an areaof the first face of the web in contact therewith to a second heatingdevice comprising a semicircular segment having a second, curved heatingface that heats an area of the second face of the web in contacttherewith, and further comprising a deflection roll for the web, andmoving the second heating device concentrically around the first suchthat the area in contact with and heated by each of the heating faces ischanged.
 2. The process according to claim 1, wherein the heating facesare heated by means of heat conduction.
 3. The process according toclaim 1, wherein the moving web is guided through a first fixed positionbefore contact with the first heating face and through a second fixedposition after contact with the second heating face.
 4. The processaccording to claim 1, wherein the web is a corrugated board web.
 5. Apreheater for a moving web having first and second faces, comprising:afirst heating device comprising a rotatable drum having a first, curvedheating face for heating an area of the first face of the web woundaround and in contact with the first heating face, a second heatingdevice comprising a semicircular segment having a second, curved heatingface for heating an area of the second face of the web wound around andin contact with the second heating face, and further comprising adeflection roll for the web, the second heating device being locatedoutside of the rotatable drum, first and second guide means for the webfixed in location upstream of the first heating device and downstream ofthe second heating device, respectively, and means for moving the secondheating device concentrically around the first heating device, such thatthe area of the web in contact with and heated by the first and secondheating faces is changed.
 6. The preheater according claim 5,additionally comprising a foot supporting the first and second heatingdevices.